The background and personal details of members of the public who have applied to appear on this Thursday's edition of the flagship BBC1 current affairs show have been subject to more stringent vetting than usual, MediaGuardian.co.uk understands.

All applicants for the Question Time audience are asked for a phone number and email address. They are also asked which party they would vote for if a general election was called tomorrow and if they fully support that party's leader.

The BBC is understood to have ensured that detailed investigations have been carried out to try to ensure a balanced audience with a range of political views, including some BNP supporters.

This Thursday, any people who have got into the audience illegally and circumvented the security checks will be asked to leave BBC Television Centre, where Question Time is being filmed.

Other changes to the usual procedures include Thursday's episode being filmed slightly earlier than usual to give extra leeway to the BBC to edit the show should there be a disturbance. Question Time is usually pre-recorded just before transmission and goes out, "as live".

The programme is also being filmed at Television Centre, for the first time in almost four years. Question Time normally travels around the country to appear in public locations.

However, anti-fascist campaigners are expected to demonstrate outside Television Centre when Griffin appears on the programme, the first time a far-right politician has been invited on the show.

Filming in Television Centre in west London makes it easier for the corporation to control who can enter the studio where Question Time will be recorded.

It is not yet known how Griffin will make his way past demonstrators, although there is speculation he will be smuggled in a car or van.

Meanwhile, BBC insiders have disputed a suggestion that there has been a lobby from the Question Time team over the past two years for Griffin to appear on Question Time.

One said: "A lot of programme-makers have had to discuss the issue as the BNP has won seats but to say there has been lobbying for him is extraordinary."

Another source added: "There have been ongoing conversations at some points like when the BNP got elected but that was it."

However, it is understood that the invitation to Griffin to take part in Question Time has divided opinion within the BBC newsroom.

• To contact the MediaGuardian news desk email editor@mediaguardian.co.uk or phone 020 3353 3857. For all other inquiries please call the main Guardian switchboard on 020 3353 2000.

• If you are writing a comment for publication, please mark clearly "for publication".